From EP 0 539 430-B1 a bioreactor is known having a reaction chamber and a mixing chamber. An inlet system allows influent and/or recycled material to enter the reactor vessel through a mixing chamber separated from the reaction chamber by a partition, the partition having slits. The mixing chamber is conically shaped and comprises steel plates welded to the interior of the reactor vessel near a bottom thereof. The inlet system provides a tangential flow in the mixing chamber.
Much of the energy necessary to bring the influent and/or recycled material in the mixing chamber is dissipated with the cyclone flow in the mixing chamber according to EP 0 539 430-B1. Still, the pressure difference over the partition is limited because of strength limitations of the partition material which causes unequal distribution of the influent in the mixing chamber and eventually in the reaction chamber. Further the pressure difference over the partition increases the level in the degassing tank connected downstream with the bioreactor.